Surgical stapling device with parallel jaw closure

ABSTRACT

A surgical stapling device includes a tool assembly and a drive assembly. The tool assembly includes an anvil assembly and a cartridge assembly that define longitudinal axes. The drive assembly is movable from a retracted position to move the tool assembly from an open position in which the longitudinal axes of the anvil and cartridge assemblies define an acute angle, to a partially clamped position in which the longitudinal axes of the anvil and cartridge assemblies are substantially parallel, and to a clamped position in which the longitudinal axes of the anvil and cartridge assemblies are substantially parallel.

FIELD

This technology is generally related to stapling devices and, more particularly, to surgical stapling devices with a tool assembly with parallel jaw closure.

BACKGROUND

Surgical stapling devices for simultaneously cutting and stapling tissue are known in the art and are commonly used during surgical procedures to reduce the time required to perform the surgical procedures and to facilitate endoscopic access to a surgical site. Performing a surgical procedure endoscopically reduces the amount of trauma inflicted on a patient during the surgical procedure to minimize patient discomfort and reduce patient recovery times.

Typically, endoscopic stapling devices include a tool assembly that has first and second jaws that are pivotally coupled at their proximal ends and can pivot in relation to each other between an open position and a clamped position. One of the jaws supports a cartridge assembly that includes a plurality of staples and the other of the jaws supports an anvil assembly. The anvil assembly includes an anvil that has staple deforming pockets that receive and form legs of the staples when the staples are ejected from the cartridge assembly.

When tissue is clamped between the first and second jaws of the tool assembly, the pivotal movement of the first and second jaws as the tool assembly is moved from the open positions towards the clamped position applies an uneven force on the tissue positioned between the anvil and cartridge assemblies that tends to extrude the tissue from a distal end of the tool assembly. The uneven force makes it difficult to monitor the force being applied to the tissue.

SUMMARY

This disclosure is directed to a surgical stapling device that includes a tool assembly and a drive assembly. The tool assembly includes an anvil assembly and a cartridge assembly that define longitudinal axes. The drive assembly is movable from a retracted position to move the tool assembly from an open position in which the longitudinal axes of the anvil and cartridge assemblies define an acute angle, to a partially clamped position in which the longitudinal axes of the anvil and cartridge assemblies are substantially parallel, and to a clamped position in which the longitudinal axes of the anvil and cartridge assemblies are substantially parallel.

An aspect of this disclosure is directed to a tool assembly including an anvil assembly, a cartridge assembly, and a drive assembly. The anvil assembly defines a first longitudinal axis and includes an inner surface positioned to engage tissue and a proximal portion. The proximal portion includes a base portion that defines a longitudinal channel and a pivot member slot. The pivot member slot extends in a direction substantially perpendicular to the longitudinal channel and includes an open end and a closed end. The cartridge assembly defines a longitudinal axis and includes a channel member and a staple cartridge. The channel member defines a cavity and a knife slot and has a proximal portion and a distal portion. The proximal portion of the channel member includes a ramp and a pivot pin positioned proximally of the ramp. The staple cartridge is received within the cavity of the channel member and includes a cartridge body, staples, pushers, and an actuation sled. The cartridge body defines a knife slot. The actuation sled is movable through the cartridge body into engagement with the pushers to eject the staples from the cartridge body. The drive assembly has a proximal portion and a distal portion and includes a flexible drive beam and a working end. The flexible drive beam has a proximal portion and a distal portion and is movably received within the longitudinal channel of the base portion of the anvil assembly. The working end is secured to the distal portion of the flexible drive beam. The proximal portion of the drive assembly defines a cam slot having a proximal portion and a distal portion. The proximal and distal portions of the cam slot define axes that intersect to define an acute angle β. The drive assembly is movable from a retracted position to an advanced position to move the working end in relation to the anvil and cartridge assemblies between retracted and advanced positions. The pivot member of the channel member is received in the pivot member slot of the anvil assembly and the cam slot of the drive assembly. The drive assembly is movable from its retracted position into engagement with the ramp of the channel member to move the tool assembly from the open position in which the first and second longitudinal axes define an acute angle, to a partially clamped position in which the first and second longitudinal axes of the anvil and cartridge assemblies are substantially parallel, and to a clamped position in which the first and second longitudinal axes of the anvil and cartridge assemblies are substantially parallel.

Another aspect of this disclosure is directed to a surgical stapling device including a handle assembly, an adapter assembly, and a tool assembly. The adapter assembly has a proximal portion and a distal portion. The proximal portion is engaged with the handle assembly. The tool assembly is pivotably supported on the distal portion of the adapter assembly and includes an anvil assembly, a cartridge assembly, and a drive assembly. The anvil assembly defines a first longitudinal axis and includes an inner surface positioned to engage tissue and a proximal portion. The proximal portion includes a base portion that defines a longitudinal channel and a pivot member slot. The pivot member slot extends in a direction substantially perpendicular to the longitudinal channel and includes an open end and a closed end. The cartridge assembly defines a longitudinal axis and includes a channel member and a staple cartridge. The channel member defines a cavity and a knife slot and has a proximal portion and a distal portion. The proximal portion of the channel member includes a ramp and a pivot pin positioned proximally of the ramp. The staple cartridge is received within the cavity of the channel member and includes a cartridge body, staples, pushers, and an actuation sled. The cartridge body defines a knife slot. The actuation sled is movable through the cartridge body into engagement with the pushers to eject the staples from the cartridge body. The drive assembly has a proximal portion and a distal portion and includes a flexible drive beam and a working end. The flexible drive beam has a proximal portion and a distal portion and is movably received within the longitudinal channel of the base portion of the anvil assembly. The working end is secured to the distal portion of the flexible drive beam. The proximal portion of the drive assembly defines a cam slot having a proximal portion and a distal portion. The proximal and distal portions of the cam slot define axes that intersect to define an acute angle β. The drive assembly is movable from a retracted position to an advanced position to move the working end in relation to the anvil and cartridge assemblies between retracted and advanced positions. The pivot member of the channel member is received in the pivot member slot of the anvil assembly and the cam slot of the drive assembly. The drive assembly is movable from its retracted position into engagement with the ramp of the channel member to move the tool assembly from the open position in which the first and second longitudinal axes define an acute angle, to a partially clamped position in which the first and second longitudinal axes of the anvil and cartridge assemblies are substantially parallel, and to a clamped position in which the first and second longitudinal axes of the anvil and cartridge assemblies are substantially parallel.

Another aspect of this disclosure is directed to a drive assembly for a surgical stapling device that includes a flexible drive beam and a working end. The flexible drive beam has a proximal portion and a distal portion. The working end is supported on the distal portion of the flexible drive beam and has an I-beam configuration. The drive assembly has a proximal portion that defines a cam slot having a proximal portion and a distal portion. The proximal and distal portions of the cam slot define axes that intersect to define an acute angle of from about 15 degrees to 75 degrees.

In aspects of the disclosure, in the open position and the partially clamped position, the pivot pin is positioned in the distal portion of the cam slot adjacent the open end of the pivot member slot, and in the clamped position, the pivot pin is positioned in the proximal portion of the cam slot adjacent the closed end of the pivot member slot.

In some aspects of the disclosure, the pivot pin is cammed from the open end of the pivot member slot towards the closed end of the pivot member slot as the pivot member moves through the proximal portion of the cam slot.

In certain aspects of the disclosure, the cam slot is defined between the distal portion of the flexible drive beam of the drive assembly and the working end of the drive assembly.

In aspects of the disclosure, the working end of the drive assembly has an I-beam configuration.

In some aspects of the disclosure, the angle β is from about 15 degrees to about 75 degrees.

In certain aspects of the disclosure, the angle β is about 45 degrees.

In aspects of the disclosure, a mounting member is secured to the base portion of the anvil assembly.

In some aspects of the disclosure, the mounting member defines a longitudinal channel that is aligned with the longitudinal channel of the base portion of the anvil assembly and receives the flexible drive beam of the drive assembly.

In certain aspects of the disclosure, the working end of the drive assembly includes a vertical strut that supports a cutting edge.

Other features of the disclosure will be appreciated from the following description.

BRIEF DESCRIPTION OF DRAWINGS

Various aspects of the disclosure are described herein below with reference to the drawings, wherein:

FIG. 1 is a side perspective view of the disclosed surgical stapling device according to aspects of the disclosure with an end effector of the surgical stapling device in an open position;

FIG. 2 is an enlarged view of the indicated area of detail shown in FIG. 1 ;

FIG. 3 is an exploded view of the end effector of the surgical stapling device shown in FIG. 1 ;

FIG. 4 is an enlarged view of the indicated area of detail shown in FIG. 3 ;

FIG. 5 is an enlarged view of the indicated area of detail shown in FIG. 3 ;

FIG. 6 is a perspective view of a proximal portion of an anvil assembly of the end effector shown in FIG. 3 ;

FIG. 7 is a side view of a working end of a drive assembly of the end effector shown in FIG. 3 ;

FIG. 8 is a side perspective view of the end effector of the surgical stapling device shown in FIG. 1 with the end effector in the open position and tissue positioned within the end effector;

FIG. 9 is an enlarged view of the indicated area of detail shown in FIG. 2 with the anvil assembly shown in phantom and an outer tube of an elongate body of the surgical stapling device removed;

FIG. 10 is a perspective view of the proximal portion of the end effector shown in FIG. 2 with the end effector in the open position;

FIG. 11 is a side view of the end effector shown in FIG. 8 with the tissue shown in cross-section;

FIG. 12 is a cross-sectional view taken along section line 12-12 of FIG. 8 with a sled and pushers removed from a staple cartridge of the end effector removed;

FIG. 13 is a side view of the end effector shown in FIG. 12 with the tissue shown in cross-section as the end effector is moved from the open position to a partially clamped position;

FIG. 14 is a longitudinal cross-sectional view taken through the end effector in the position shown in FIG. 13 ;

FIG. 15 is a side view of the end effector shown in FIG. 13 with the tissue shown in cross-section with the end effector in the clamped position; and

FIG. 16 is a longitudinal cross-sectional view taken through the end effector shown in FIG. 15 in the clamped position.

DETAILED DESCRIPTION

The disclosed surgical stapling device will now be described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. However, it is to be understood that aspects of the disclosure described herein are merely exemplary of the disclosure and may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the disclosure in virtually any appropriately detailed structure.

In this description, the term “proximal” is used generally to refer to that portion of the device that is closer to a clinician, while the term “distal” is used generally to refer to that portion of the device that is farther from the clinician. In addition, the term “endoscopic” is used generally used to refer to endoscopic, laparoscopic, arthroscopic, and/or any other procedure conducted through a small diameter incision or cannula. Further, the term “clinician” is used generally to refer to medical personnel including doctors, nurses, and support personnel. As used herein, the term “substantially parallel” includes true parallel as well as 10 degrees in either direction. In addition, directional terms such as front, rear, upper, lower, top, bottom, distal, proximal, and similar terms are used to assist in understanding the description and are not intended to limit the disclosure.

FIG. 1 illustrates exemplary aspects of the disclosed surgical stapling device shown generally as stapling device 10. Stapling device 10 includes a powered handle assembly 12, an elongate body 14, and an end effector or tool assembly 16. The elongate body 14 defines a longitudinal axis “X” and includes a proximal portion 14 a supported on the handle assembly 12 and a distal portion 14 b that supports the tool assembly 16. In some aspects of the disclosure, the tool assembly 16 forms part of a reload assembly 18 that includes a proximal body portion 18 a that is releasably coupled to the distal portion 14 b of the elongate body 14 of the stapling device 10. The proximal body portion 18 a includes a distal portion that supports the tool assembly 16. The tool assembly 16 is pivotably coupled to the proximal body portion 18 a to facilitate articulation of the tool assembly 16 about an axis transverse to the longitudinal axis “X” of the elongate body 14. Although the stapling device 10 is shown to include a removable reload assembly 18, it is envisioned that the tool assembly 16 could be secured to the distal portion 14 b of the elongate body 14.

The handle assembly 12 of the stapling device 10 includes a stationary handle 20 and actuation buttons 22 that can be depressed to actuate the tool assembly 16, e.g., approximate the tool assembly 16, articulate the tool assembly 16, fire staples, etc. In aspects of the disclosure, batteries (not shown) are supported in the stationary handle 20 to power the handle assembly 12. It is envisioned that the stapling device 10 need not be powered but can also include a manually powered handle assembly such as described in, e.g., U.S. Pat. No. 6,241,139 (“the '139 patent”). It is also envisioned that the tool assembly 16 could be incorporated onto a robotic system.

FIGS. 2-7 illustrate the tool assembly 16 of the stapling device 10 which includes an anvil assembly 26 and a cartridge assembly 28 that are movable in relation to each other between open and clamped positions. The anvil assembly 26 includes a base member 30 and an anvil plate 32. The anvil plate 32 includes an elongate body 34 that has an outer surface 36 and an inner surface 38 that faces the cartridge assembly 28. The outer surface 36 of the anvil plate 32 defines a longitudinally extending cavity 40 that extends through a proximal end of the anvil plate 32 to a position near the distal end of the anvil plate 32. The anvil plate 32 also defines a longitudinally extending knife slot 42 that extends through the anvil plate 32 from the outer surface 36 to the inner surface 38 and is centrally located within the cavity 40. The inner surface 38 (FIG. 10 ) of the anvil plate 32 is positioned to engage tissue and includes a plurality of staple forming pockets 38 a (FIG. 10 ) that receive and form staples of the cartridge assembly 28.

The base member 30 of the anvil assembly 26 includes a distal cover portion 44, a proximal base portion 46, and spaced wings 48. The cover portion 44 is secured to the anvil plate 32 over the cavity 40 of the anvil plate 32 to enclose and define a channel (not shown) within the anvil assembly 26. The channel (not shown) defined within the anvil assembly 26 receives a portion of a working end of a drive assembly 100 (FIG. 3 ) which is described below. The spaced wings 48 are positioned between the cover portion 44 and the base portion 46 and extend from the anvil assembly 26 towards and past the cartridge assembly 28 to define tissue stops. The wings 48 cover the proximal portion of the cavity 40 of the anvil plate 32 to define a proximal portion of the channel (not shown) defined by the anvil assembly 26.

The base portion 46 of the base member 30 of the anvil assembly 26 includes a body 50 that defines a centrally located longitudinally extending channel 52, a pivot member slot 54 (FIG. 6 ) that extends in a direction substantially perpendicular to the channel 52 (FIG. 6 ), and a pivot member 56 (FIG. 3 ) positioned on an outer surface of the body 50. The channel 52 receives the drive assembly 100 (FIG. 3 ) of the stapling device 10 which is described below and has a diverging proximal portion 52 a that facilitates bending of the drive assembly 100 when the tool assembly 16 is articulated. The slot 54 has a first open end 54 a that faces the cartridge assembly 28 and a second closed end 54 b. The pivot member 56 defines an axis that is transverse to a longitudinal axis “Y” (FIG. 15 ) of the tool assembly 16 when the tool assembly 16 is in the clamped position.

The cartridge assembly 28 includes a channel member 60 and a staple cartridge 62 that includes a cartridge body 62 a, staples 64 (FIG. 3 ), pushers 66 (FIG. 3 ), and an actuation sled 68 (FIG. 3 ). The channel member 60 defines a longitudinally extending cavity 70 that receives the staple cartridge 62. In aspects of the disclosure, the staple cartridge 62 is releasable from the cavity 70 to facilitate replacement of the staple cartridge 62 after each firing of the stapling device 10 (FIG. 1 ) to facilitate reuse of the stapling device 10. The cartridge body 62 a defines a central knife slot 74 and staple receiving pockets 76 positioned on each side of the central knife slot 74. In aspects of the disclosure, the staple receiving pockets 76 are aligned in rows on each side of the central knife slot 74 and include open ends that face the anvil assembly 26 when the tool assembly 16 is in a clamped position. The staples 64 and the pushers 66 are received in each of the staple receiving pockets 76 of the cartridge body 62 a. The actuation sled 68 is received within the cartridge body 62 a and includes cam members 68 a that are aligned with the pushers 66. The actuation sled 68 is movable within the cartridge body 62 a from a retracted position to an advanced position to drive the pushers 66 towards the open end of the staple receiving pockets 76 to eject the staples 64 from the staple receiving pockets 76 of the cartridge body 62 a. The '139 patent describes the interaction of the actuation sled and pushers in further detail.

The channel member 60 defines a knife slot 60 a and includes a ramp 78 (FIG. 3A) and proximal extensions 80 that extend from opposite sides of the channel member 60. The ramp 78 is engaged by the drive assembly 100 as described below to move the tool assembly 16 from the open position (FIG. 2 ) to a partially clamped position (FIG. 13 ), and subsequently to the clamped position (FIG. 15 ). The proximal extensions 80 support a pivot pin 82 that extends between the proximal extensions 80 and is received in the slot 54 in the body 50 of the base portion 46 of the anvil assembly 26 (FIG. 3 ). An outer surface 60 b (FIG. 3A) of the channel member 60 defines a channel 63 that receives a portion of the drive assembly 100 (FIG. 3 ) as described below.

FIGS. 3, 5, and 7 illustrate the distal portion of a drive assembly 100 that includes a flexible drive beam 102 and a working end 104. The flexible drive beam 102 has a proximal end (not shown) that is coupled to a driver in the elongate body 14 (FIG. 1 ) and a distal end 106 that is secured to the working end 104. In aspects of the disclosure, the working end 104 of the drive assembly 100 has an I-beam configuration that includes a first beam 108, a second beam 110, and a vertical strut 112 that connects the first beam 108 to the second beam 110. The first beam 108 is received within the channel (not shown) defined within the anvil assembly 26 and the second beam 110 is aligned with and positioned proximally of the ramp 78 of the channel member 60 of the cartridge assembly 28 when the drive assembly 100 is in a retracted position and is received in the channel 63 of the channel member 60 when the tool assembly 16 is in the clamped position. The drive assembly 100 is movable in relation to the tool assembly 16 to move the tool assembly 16 from the open position to the clamped position and to advance the actuation sled 68 through the staple cartridge 62 to eject the staples 64 from the staple cartridge 62. In aspects of the disclosure, the vertical strut 112 includes or supports a cutting edge 114 that extends through the knife slots 42 and 62 of the anvil assembly 26 and the cartridge assembly 28, respectively, and the knife slot 60 a of the channel member 60. The cutting edge 114 is positioned to cut tissue clamped between the anvil and cartridge assemblies 26 and 28, respectively.

The distal portion of the drive assembly 100 defines a cam slot 120 (FIG. 7 ) that has a distal portion 120 a that defines an axis “Z1” (FIG. 7 ) that is parallel to or coaxial with the longitudinal axis “Y” (FIG. 15 ) of the tool assembly 16 and a proximal portion 120 b that defines an axis “Z2” that defines an acute angle β with the axis “Z1”. In aspects of the disclosure, angle β is from about 15 degrees to about 75 degrees and can be about 45 degrees. In one aspect of the disclosure, the cam slot 120 is defined between a proximal surface of the working end 104 of the drive assembly 100 and a distal portion of the flexible drive beam 102 of the drive assembly 100.

The surgical stapling device 10 includes a mounting member 130 (FIG. 3 ) that defines a central longitudinally extending slot 132 that has a diverging proximal portion 132 a. The mounting member 130 includes a pivot member 134 (FIG. 10 ) and is secured to the base portion 46 of the base member 30 of the anvil assembly 26 using screws 131 (FIG. 3 ) such that the flexible drive beam 102 is received between the base portion 46 and the mounting member 130 within the slot 54 of the base portion 46 and the slot 132 (FIG. 3 ) in the mounting member 130.

The tool assembly 16 is secured to the elongate body 14 of the stapling device 10 (FIG. 1 ) by coupling members 140 a and 140 b (FIG. 3 ). The coupling member 140 a is fixedly secured to the elongate body 14 (FIG. 1 ) and pivotably coupled to the pivot member 56 of the base portion 46 of the anvil assembly 26. The coupling member 140 b is fixedly secured to the elongate body 14 (FIG. 1 ) and pivotably coupled to the pivot member 134 (FIG. 12 ) of the mounting member 130. The pivot members 56 and 134 define a pivot axis “S” (FIG. 12 ) that is substantially perpendicular to the longitudinal axis “Y” of the tool assembly 16 when the tool assembly 16 is in the clamped position.

FIGS. 8-12 illustrate the tool assembly 16 in the open position with tissue “T” positioned between the anvil and cartridge assemblies 26 and 28, respectively, and the drive assembly 100 in its retracted position. When the drive assembly 100 is in its retracted position, the working end 104 of the drive assembly 100 is positioned distally of and in abutting relation to the proximal base portion 46 of the base member 30 of the anvil assembly 26. In this position, the pivot pin 82 on the proximal portion of the channel member 60 is positioned in the distal end 120 a of the cam slot 120 in the distal portion of the drive assembly 100. As best seen in FIG. 12 , the distal portion 120 a of the cam slot 120 retains the pivot pin 82 near the first open end 54 a of the slot 54 in the base portion 46 of the anvil assembly 26. With the pivot pin 82 in this position, the cartridge assembly 28 is retained in the open position in which a longitudinal axis of the cartridge assembly 28 is at an angle to the longitudinal axis of the anvil assembly 26 to define an open mouth 160 (FIG. at the distal end of the tool assembly 16.

FIGS. 13 and 14 illustrate the tool assembly 16 in a partially clamped position with the tissue “T” partially clamped between the anvil and cartridge assemblies 26 and 28 and the drive assembly 100 advanced to a position in which the working end 104 of the drive assembly 100 has engaged and moved over a portion of the ramp surface 78 of the channel member 60 to pivot the cartridge assembly 28 in the direction indicated by arrow “A in FIG. 13 to a position in which the longitudinal axis of the cartridge assembly 28 is substantially parallel to the longitudinal axis of the anvil assembly 26. When the drive assembly 100 is advanced in the direction indicated by arrows “B” in FIG. 14 to move the tool assembly 16 to the partially clamped position, the pivot pin 82 on the proximal portion of the channel member 60 of the cartridge assembly 28 is positioned in the proximal end of the distal portion 120 a of the cam slot 120 in the distal portion of the drive assembly 100. In this position, the cam slot 120 still retains the pivot pin 82 near the first open end 54 a of the slot 54 in the base portion 46 of the anvil assembly 26 to allow the cartridge assembly 28 to pivot to the position in which the longitudinal axes of the cartridge assembly 28 and the anvil assembly 26 are parallel and in spaced opposition. As illustrated in FIG. 14 , the angle of the ramp 78 and the is substantially the same is the angle of the proximal portion 120 b of the cam slot 120.

FIGS. 15 and 16 illustrate the tool assembly 16 in the clamped position with the tissue “T” clamped between the anvil and cartridge assemblies 26 and 28, respectively, and the drive assembly 100 advanced to a position in which the second beam 110 of the working end 104 of the drive assembly 100 is positioned adjacent the distal end of the ramp 78 of the channel member 60 in alignment with the channel 63 in the channel member 60. As the drive assembly 100 is advanced in the direction indicated by arrows “B” in FIG. 16 to move the tool assembly 16 to the clamped position, the pivot pin 82 on the proximal portion of the channel member 60 moves into the proximal portion 120 b of the cam slot 120 in the distal portion of the drive assembly 100. The distal portion 120 b of the cam slot 120 defines the acute angle β (FIG. 7 ) with the distal portion 120 a of the cam slot 120. When the pivot pin 82 enters the proximal portion 120 b of the cam slot 120, further advancement of the drive assembly 100 cams the pivot pin 82 towards the closed end 54 b of the slot 54 in the base portion 46 of the anvil assembly 26 to move the cartridge assembly 28 in the direction indicated by arrows “C” in FIG. 16 toward the anvil assembly 26. Confinement of the pivot member 82 within the slot 54 and engagement of the second beam 110 of the working end 102 of the drive assembly 100 with the channel member 60 of the cartridge assembly 28 moves the cartridge assembly 28 towards the anvil assembly 26 with the longitudinal axes of the anvil and cartridge assemblies 26 and 28 remaining in substantially parallel relation to effect parallel closure of the tool assembly 16.

Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary aspects of the disclosure. It is envisioned that the elements and features illustrated or described in connection with one exemplary embodiment may be combined with the elements and features of another without departing from the scope of the present disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described aspects of the disclosure. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. 

What is claimed is:
 1. A tool assembly comprising: an anvil assembly defining a first longitudinal axis, the anvil assembly including an inner surface positioned to engage tissue and a proximal portion, the proximal portion including a base portion defining a longitudinal channel and a pivot member slot, the pivot member slot extending in a direction substantially perpendicular to the longitudinal channel and including an open end and a closed end; a cartridge assembly defining a second longitudinal axis, the cartridge assembly including a channel member and a staple cartridge, the channel member defining a cavity and a knife slot and having a proximal portion and a distal portion, the proximal portion of the channel member including a ramp and a pivot member positioned proximally of the ramp, the staple cartridge received within the cavity of the channel member and including a cartridge body, staples, pushers, and an actuation sled, the cartridge body defining a knife slot, the actuation sled movable through the cartridge body into engagement with the pushers to eject the staples from the cartridge body; and a drive assembly having a proximal portion and a distal portion and including a flexible drive beam and a working end, the flexible drive beam having a proximal portion and a distal portion and being movably received within the longitudinal channel of the base portion of the anvil assembly, the working end secured to the distal portion of the flexible drive beam, the distal portion of the drive assembly defining a cam slot having a proximal portion and a distal portion, the proximal and distal portions of the cam slot defining axes that intersect to define an acute angle β, the drive assembly movable from a retracted position to an advanced position to move the working end in relation to the anvil and cartridge assemblies between retracted and advanced positions and move the actuation sled through the cartridge body to eject the staples from the cartridge body; wherein the pivot member of the channel member is received in the pivot member slot of the anvil assembly and the cam slot of the drive assembly, and the drive assembly is movable from its retracted position into engagement with the ramp of the channel member to move the tool assembly from the open position in which the first and second longitudinal axes define an acute angle, to a partially clamped position in which the first and second longitudinal axes of the anvil and cartridge assemblies are substantially parallel, and to a clamped position in which the first and second longitudinal axes of the anvil and cartridge assemblies are substantially parallel.
 2. The tool assembly of claim 1, wherein in the open position and the partially clamped positions, the pivot member is positioned in the distal portion of the cam slot adjacent the open end of the pivot member slot, and in the clamped position, the pivot member is positioned in the proximal portion of the cam slot adjacent the closed end of the pivot member slot.
 3. The tool assembly of claim 2, wherein the pivot member is cammed from the open end of the pivot member slot towards the closed end of the pivot member slot as the pivot member moves through the proximal portion of the cam slot.
 4. The tool assembly of claim 1, wherein the cam slot is defined between the distal portion of the flexible drive beam of the drive assembly and the working end of the drive assembly.
 5. The tool assembly of claim 1, wherein the working end of the drive assembly has an I-beam configuration.
 6. The tool assembly of claim 5, wherein the working end of the drive assembly includes a vertical strut that supports a cutting edge.
 7. The tool assembly of claim 1, wherein the angle β is from about 15 degrees to about 75 degrees.
 8. The tool assembly of claim 7, wherein the angle β is about 45 degrees.
 9. The tool assembly of claim 1, further including a mounting member secured to the base portion of the anvil assembly, the mounting member defining a longitudinal channel that is aligned with the longitudinal channel of the base portion of the anvil assembly and receives the flexible drive beam of the drive assembly.
 10. A surgical stapling device comprising: a handle assembly; an adapter assembly having a proximal portion and a distal portion, the proximal portion engaged with the handle assembly; and a tool assembly pivotably supported on the distal portion of the adapter assembly, the tool assembly including: an anvil assembly defining a first longitudinal axis, the anvil assembly including an inner surface positioned to engage tissue and a proximal portion, the proximal portion including a base portion defining a longitudinal channel and a pivot member slot, the pivot member slot extending in a direction substantially perpendicular to the longitudinal channel and including an open end and a closed end; a cartridge assembly defining a second longitudinal axis, the cartridge assembly including a channel member and a staple cartridge, the channel member defining a cavity and a knife slot and having a proximal portion and a distal portion, the proximal portion of the channel member including a ramp and a pivot member positioned proximally of the ramp, the staple cartridge received within the cavity of the channel member and including a cartridge body, staples, pushers, and an actuation sled, the cartridge body defining a knife slot, the actuation sled movable through the cartridge body into engagement with the pushers to eject the staples from the cartridge body; and a drive assembly having a proximal portion and a distal portion and including a flexible drive beam and a working end, the flexible drive beam having a proximal portion and a distal portion and being movably received within the longitudinal channel of the base portion of the anvil assembly, the working end secured to the distal portion of the flexible drive beam, the distal portion of the drive assembly defining a cam slot having a proximal portion and a distal portion, the proximal and distal portions of the cam slot defining axes that intersect to define an acute angle β, the drive assembly movable from a retracted position to an advanced position to move the working end in relation to the anvil and cartridge assemblies between retracted and advanced positions; wherein the pivot member of the channel member is received in the pivot member slot of the anvil assembly and the cam slot of the drive assembly, and the drive assembly is movable from its retracted position into engagement with the ramp of the channel member to move the tool assembly from the open position in which the first and second longitudinal axes define an acute angle, to a partially clamped position in which the first and second longitudinal axes of the anvil and cartridge assemblies are substantially parallel, and to a clamped position in which the first and second longitudinal axes of the anvil and cartridge assemblies are substantially parallel.
 11. The surgical stapling device of claim 10, wherein in the open position and the partially clamped positions, the pivot member is positioned in the distal portion of the cam slot adjacent the open end of the pivot member slot, and in the clamped position, the pivot member is positioned in the proximal portion of the cam slot adjacent the closed end of the pivot member slot.
 12. The surgical stapling device of claim 11, wherein the pivot member is cammed from the open end of the pivot member slot towards the closed end of the pivot member slot as the pivot member moves through the proximal portion of the cam slot.
 13. The surgical stapling device of claim 10, wherein the cam slot is defined between the distal portion of the flexible drive beam of the drive assembly and the working end of the drive assembly.
 14. The surgical stapling device of claim 10, wherein the working end of the drive assembly has an I-beam configuration.
 15. The surgical stapling device of claim 14, wherein the working end of the drive assembly includes a vertical strut that supports a cutting edge.
 16. The surgical stapling device of claim 10, wherein the angle β is from about 15 degrees to about 75 degrees.
 17. The surgical stapling device of claim 16, wherein the angle β is about 45 degrees.
 18. The surgical stapling device of claim 10, further including a mounting member secured to the base portion of the anvil assembly, the mounting member defining a longitudinal channel that is aligned with the longitudinal channel of the base portion of the anvil assembly and receives the flexible drive beam of the drive assembly.
 19. A drive assembly for a surgical stapling device comprising: a flexible drive beam and a working end, the flexible drive beam having a proximal portion and a distal portion, the working end secured to the distal portion of the flexible drive beam and having an I-beam configuration, wherein the drive assembly has a distal portion that defines a cam slot having a proximal portion and a distal portion, the proximal and distal portions of the cam slot defining axes that intersect to define an acute angle of from about 15 degrees to 75 degrees, wherein the cam slot is formed by the distal portion of the flexible drive beam and a proximal surface of the working end. 